The Alamoutala carbonate-hosted gold deposit, Kédougou-Kénieba inlier, West Africa

Quentin Masurel, Nicolas Thébaud, John Miller, Stanislav Ulrich, Malcolm Peter Roberts, Didier Béziat

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The Alamoutala gold deposit is located in the Kédougou-Kénieba inlier, a window of Paleoproterozoic rocks that crop out in eastern Senegal and western Mali. The deposit is part of the ∼3-Moz Au Yatela district and produced 308,400 oz Au between 2002 and 2012. Country rocks in the Alamoutala open pit consist of carbonate rocks, arenites, wackes, and siltstones. The sedimentary rocks have been subjected to polycyclic deformation and regional greenschist-facies metamorphism. Synkinematic, calc-alkaline, intermediate quartz-feldspar porphyry stocks intruded the metasedimentary rocks at 2083 ± 7 Ma (U-Pb zircon). Amphibolite-facies contact metamorphism of carbonate rocks resulted in the formation of a high-temperature-low-pressure magnetitebearing skarn. Field relationships and microtextural data, however, indicate that economic gold mineralization is shear hosted and occurred during retrograde contact metamorphism. Geometric and kinematic analyses indicate that the ore-hosting structures were undergoing sinistral-reverse displacement at the time of mineralization. Ore minerals deposited synchronous with a potassic hydrothermal alteration assemblage defined as biotite + calcite + pyrite ± K-feldspar, actinolite-tremolite, quartz, muscovite, and tourmaline. Petrographic studies reveal that ore-related sulfides largely consist of pyrite with lesser pyrrhotite and chalcopyrite. The ore also contains accessory Ag-Sb-As-Hg-Bi-Te-Mo-W-Zn-Pb-Ni-Co-U-bearing mineral species. The Alamoutala deposit represents two distinct hydrothermal systems in which a locally developed magnetite-bearing skarn was overprinted by a region-wide orogenic gold event in the late Eburnean.

Original languageEnglish
Pages (from-to)49-72
Number of pages24
JournalEconomic Geology
Volume112
Issue number1
DOIs
Publication statusPublished - 1 Jan 2017

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Gold deposits
inlier
Carbonates
carbonates
contact metamorphism
gold
deposits
skarn
Rocks
Ores
minerals
carbonate
carbonate rock
Bearings (structural)
rocks
feldspar
pyrite
Quartz
mineralization
quartz

Cite this

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title = "The Alamoutala carbonate-hosted gold deposit, K{\'e}dougou-K{\'e}nieba inlier, West Africa",
abstract = "The Alamoutala gold deposit is located in the K{\'e}dougou-K{\'e}nieba inlier, a window of Paleoproterozoic rocks that crop out in eastern Senegal and western Mali. The deposit is part of the ∼3-Moz Au Yatela district and produced 308,400 oz Au between 2002 and 2012. Country rocks in the Alamoutala open pit consist of carbonate rocks, arenites, wackes, and siltstones. The sedimentary rocks have been subjected to polycyclic deformation and regional greenschist-facies metamorphism. Synkinematic, calc-alkaline, intermediate quartz-feldspar porphyry stocks intruded the metasedimentary rocks at 2083 ± 7 Ma (U-Pb zircon). Amphibolite-facies contact metamorphism of carbonate rocks resulted in the formation of a high-temperature-low-pressure magnetitebearing skarn. Field relationships and microtextural data, however, indicate that economic gold mineralization is shear hosted and occurred during retrograde contact metamorphism. Geometric and kinematic analyses indicate that the ore-hosting structures were undergoing sinistral-reverse displacement at the time of mineralization. Ore minerals deposited synchronous with a potassic hydrothermal alteration assemblage defined as biotite + calcite + pyrite ± K-feldspar, actinolite-tremolite, quartz, muscovite, and tourmaline. Petrographic studies reveal that ore-related sulfides largely consist of pyrite with lesser pyrrhotite and chalcopyrite. The ore also contains accessory Ag-Sb-As-Hg-Bi-Te-Mo-W-Zn-Pb-Ni-Co-U-bearing mineral species. The Alamoutala deposit represents two distinct hydrothermal systems in which a locally developed magnetite-bearing skarn was overprinted by a region-wide orogenic gold event in the late Eburnean.",
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The Alamoutala carbonate-hosted gold deposit, Kédougou-Kénieba inlier, West Africa. / Masurel, Quentin; Thébaud, Nicolas; Miller, John; Ulrich, Stanislav; Roberts, Malcolm Peter; Béziat, Didier.

In: Economic Geology, Vol. 112, No. 1, 01.01.2017, p. 49-72.

Research output: Contribution to journalArticle

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